Atlanta - Speakers honouring the Rev Martin Luther King jnr at his spiritual home in Atlanta repeated the same message on his national holiday on Monday: We've come a long way, but there's still much to be done to fulfil the slain civil rights activist's dream.The holiday came against the backdrop of recent nationwide protests over the deaths of unarmed black men and boys at the hands of police around the country.King's daughter, the Rev Bernice King, urged those gathered at Ebenezer Baptist Church in Atlanta for the 47th annual Martin Luther King jnr Annual Commemorative Service to act out against injustice. But she also said they should heed her father's message of nonviolence.Nonviolent coexistence"We cannot act unless we understand what Dr King taught us. He taught us that we still have a choice to make: nonviolent coexistence or violent co-annihilation," she said. "I challenge you to work with us as we help this nation choose nonviolence."She invoked the deaths of unarmed black men in Ferguson, Missouri, and in New York City and the fatal shooting of a 12-year-old boy in Cleveland, Ohio. All three were killed by white officers."I cannot help but remember many women and men who have been gunned down, not by a bad police force but by some bad actors in a police force," she said.The Northeast Ohio Media Group reported about 60 people gathered on Monday at a recreation centre where a Cleveland police officer fatally shot the 12-year-old. Their march ended at the city's public square and police told the group some arrests were made.'Black lives matter'In Seattle, authorities reported a handful of arrests after dozens chanting "black lives matter" disrupted traffic in Seattle, blocking part of a state highway and interstate off-ramps. Seattle officials advised motorists to take alternate routes when one side of a key state route was temporarily blocked.The shootings of unarmed blacks sparked protests and debate over police use of force. The tensions grew after two New York City police officers were shot to death last month by a man who suggested in online posts that he was retaliating for the deaths of Michael Brown in Ferguson and Eric Garner in New York. The gunman, who was black, committed suicide.Six months after Garner died in a white police officer's chokehold, protests and speeches invoking Garner's name provided a backdrop to King tributes in New York.New York Mayor Bill de Blasio had supported the demonstrations that followed a grand jury's decision not to indict the officer in Garner's death, fracturing his relationship with the city's police unions. Yet he vowed on Monday that New York would emerge a more unified city."We will move forward as a city. We will move forward to deeper respect for all," de Blasio said at the annual MLK Day event at the Brooklyn Academy of Music, his city's largest tribute.President Barack Obama, America's first black president, sought to focus on the next generation. In Washington, Obama and his wife Michelle went with one of their daughters, Malia, to a site for the Boys and Girls Clubs of Greater Washington to paint murals and assemble "literacy kits" of flashcards and books to help youngsters improve their reading and writing skills.SelmaEarlier in Atlanta, actor David Oyelowo said playing King in the film Selma was deeply emotional and a heavy burden to bear."I felt his pain. I felt his burden. I felt the love he had for his family. I felt the love he still has for you Dr Bernice King," he said, addressing King's daughter.Oyelowo cried as he talked about putting himself in King's place. "I only stepped into his shoes for a moment, but I asked myself, 'How did he do it?'" Oyelowo said. He explained that he, like King, has four children and said he cannot imagine walking through life knowing there are people who wanted to take their lives or that of his wife.US Representative John Lewis told the Atlanta crowd he was just 17 when King sent him a bus ticket to head to Alabama to join the civil rights movement. Lewis, who marched alongside King, recalled the man he called his hero a man who is "still a guiding light in my life"."The memory of such a great man can never, ever fade," Lewis said. "I still think about him almost every day."